464 Hawkins — Notes on the Geology of Rhode Island. 



Five analyses of rocks from Neutaconkanut Hill are 

 given in Table III (analyses 13, 16, 17, 18, 19) and three 

 from Berkeley (analyses 14, 21, 22). Analysis 13 

 was made npon material taken at a point about 100 feet 

 from the granite, and represents an apparently little 

 altered green schist, while the rock of analysis 16 has a 

 typically coarse speckled appearance, giving it a dioritic 

 aspect ; it was taken from within 25 feet of the contact. 

 The "xenolith" of schist was found as a well-defined 

 dark-colored inclusion in the granite, which lies close 

 together with several other xenoliths in the ledge at a 

 point nearly 50 feet from the nearest green schist out- 

 crop. The granite of analysis 18 is mapped as Milford 

 granite by Emerson and Perry, on the southeast flank of 

 the hill. It is abnormally dark-colored and is filled with 

 closely spaced chunky phenocrysts of secondary feldspar. 

 It is about 20 feet from the green schist contact. The 

 nearest granite that is free from inclusions and abnormal 

 dark color, with which the above intrusive can be com- 

 pared, is at Hughesdale, a mile and a half west (analysis 

 19). This latter type is fully 1000 feet from the nearest 

 included rock, which is a quartzite, and seems to be a type 

 of the Milford granite gneiss free from any large amount 

 of foreign substances. 



The exposures at Berkeley are not so satisfactory in 

 character, but the same phenomena are strongly devel- 

 oped. The rock represented by analysis 14 is at least 

 200 feet from the granite ; that of analysis 21, the pseudo- 

 diorite, is about 100 feet from it. The granite is dark 

 and porphyritic, but zenoliths suitable for analysis were 

 not found. There is also no granite in the vicinity free 

 from schist. 



Comparison of the analyses shows what appears to be a 

 unity of action in the exchange of elements by pneumat- 

 olysis during this contact metamorphism. Alumina 

 becomes segregated somewhere near the contact, as does 

 also soda and to some extent potash (although appar- 

 ently not enough to form much biotite, as has been gen- 

 erally supposed). Ferric iron is very largely reduced 

 to the ferrous state and magnetite appears, both in the 

 granite and in the invaded rocks (especially noticeable in 

 the case of the wall rocks surrounding some Rhode Island 

 pegmatites). It is interesting to note that W. Gr. Foye, 

 in a recent publication concerning the contact action of 



